A new class of phenol aralkylation polymers was recently described.
These polymers exhibit improved oil solubility, improved compatibility with oil and alkyd-based polymers, urethanes, and epoxies, and a decreased tendency to form color bodies that darken coatings derived from the phenol aralkylation polymers. One way to make the phenol aralkylation polymers is to first aralkylate a phenolic monomer (such as bisphenol A) with a styrene derivative to obtain an aralkylated phenol, and then react the aralkylated phenol with an aryl diolefin to produce the phenol aralkylation polymer. This reaction scheme is illustrated in the simplified scheme below: ##STR1##
As those skilled in the art will appreciate, these polymers are actually complex mixtures that contain many structural analogs of the compounds pictured above. The types of structures actually present, of course, depend greatly upon the relative proportions of phenolic monomer, styrene derivative, and aryl diolefin.
Phenol aralkylation polymers can be made by first reacting the phenolic monomer with an aryl diolefin to obtain a phenol/aryl diolefin polymer, and then aralkylating the phenol/aryl diolefin polymer with a styrene derivative to obtain a phenol aralkylation polymer. In this case, the phenolic component is joined to the aryl diolefin with at least a portion of the phenolic linkages para to the phenolic hydroxyl groups. This process, which produces a phenol aralkylation polymer having a higher melting point, is shown in the simplified scheme below: ##STR2##
The phenol aralkylation polymers described above have many advantages compared with standard phenolics, including good solubility, good compatibility, and low discoloration. Improved solubility in nonpolar solvents is a direct consequence of styrene component addition, as is the improved compatibility with other typical resin systems, including epoxies, acrylates, styrenics, and the like. Lower rates of discoloration compared with phenolics result from the absence of dihydromethylene linkages.
The usefulness of phenol aralkylation polymers, however, is somewhat limited by the presence of only phenolic hydroxyl groups. For example, the usefulness of phenol aralkylation polymers in the coating and adhesive product areas is limited by the inability of phenolic hydroxyl groups to react either with organic acids to form esters, or with esters to form new esters by transesterification. The esterification and transesterification reactions require aliphatic hydroxyl groups. In addition, phenol aralkylation polymers having only phenolic hydroxyl groups will not react with maleic anhydride to produce unsaturated polyesters. In sum, although the limited reactivity of phenol aralkylation polymers does not preclude their use in coatings and adhesives, it does restrict their usefulness in these applications.